IES TM-30-20 PREFERENCE

The Annex to the Technical Memorandum TM-30-20 describes a new concept: Intent. This adds flexibility for different end user applications. Instead of the familiar two valued CRI Ra, R9 style criteria, TM-30-20 Design Intent descriptions have three metrics and three levels of priority:

• Preference – subjective evaluations of pleasantness, naturalness, acceptability, and related qualities.
• Vividness – subjective evaluations of color vividness, vibrancy or saturation.
• Fidelity – objective quantification of color fidelity. Average color fidelity measures such as TM-30-18 Rf quantify the average color shift in comparison to a reference illuminant.

For intent ratings below priority level 3, a minus sign is used (P-, V-, F-). If your intent is a very high energy efficiency, you will need to use products with P-, V-, F- intent ratings. White LEDs with Ra values below 80 typically have minus fidelity ratings in this system but better lumens per watt compared to premium color fidelity LED products. This is a consequence of the poor eye response to red light. High CRI requires higher red content which decreases the lumens per watt of a white LED.

Here are examples of color vector graphics for some light sources.

Links to additional information and resources about IES TM-30-20

Free download of the ANSI/IES  TM-30-20